Auxiliary power units (APUs) are commonly deployed on aircraft to provide an efficient source of electrical power, pressurized air, and/or hydraulic pressure. A representative APU includes a housing in which an engine (e.g., a gas turbine engine), an engine control unit (ECU), and an electrical generator are disposed. The ECU controls various operational parameters of the engine, which, in turn, drives the generator to produce electricity. A number of modular components, commonly referred to as “line replaceable units” or simply “LRUs,” are removably mounted to the APU and perform various functions. A non-exhaustive list of LRUs includes heat exchangers, pumps (e.g., oil pumps, fuel pumps and fuel controls, etc.), cooling fans, valves (e.g., surge control valves, fuel metering valves, bleed air valves, etc.), starter motors, transducers (e.g., temperature transducers, pressure transducers, etc.), ignition control units, and wiring harnesses. The ECU is a readily-replaceable component of the APU and may thus also be considered an LRU. LRUs are distinct from the core components of the APU (e.g., the compressor sections, the combustor section, and the turbine sections of a gas turbine engine) due to their ability to be individually replaced during routine maintenance procedures. Indeed, over its operational lifetime, a single LRU may be deployed upon a number of different APUs and, therefore, a number of different aircraft.
It is desirable to monitor operational data pertaining to line replaceable units for multiple reasons. Inspection and maintenance milestones may be based upon an LRU's accumulated operating time (referred to herein as “operating hours” or simply “hours”) or an LRU's accumulated cycles (e.g., start cycles, thermal cycles, etc.). An LRU's accumulated operating hours and cycles may also determine whether or not a manufacturer's warranty is still in force. In addition to operational data, it may also be desirable to monitor certain environmental conditions (e.g., temperatures, vibrations, pressurizes, etc.) to which an LRU is exposed for warranty and diagnostic purposes (e.g., failure analysis).
LRU operational data is conventionally monitored via manual record keeping procedures (e.g., the creation of hand-written log books or computer data files). However, due to the modular nature of LRUs, conventional manual record keeping procedures are time consuming, costly, and subject to human error. If available, a manually-created record may be inaccurate or incomplete and consequently may be of little use in verifying of a warranty claim or locating a recalled LRU. Furthermore, conventional record keeping procedures do not provide a means for monitoring characteristics (e.g., temperatures, vibrations, pressures, etc.) of an LRU's operational environment.
It should thus be appreciated that it would be desirable to provide an LRU data recorder and storage system capable of storing operational data and, perhaps, identification and maintenance information pertaining to one or more line replaceable units. Preferably, such a data recorder and storage system would also be capable of monitoring and storing data relating to the characteristics of the environment in which the LRU operates. Finally, it would also be desirable to provide a data recorder and storage system capable of storing maintenance and identification information relating to the LRU, the host APU (e.g., the APU serial number), and/or the aircraft on which the LRU is deployed (e.g., the aircraft tail number). Other desirable features and characteristics of the present invention will become apparent from the subsequent Detailed Description and the appended claims, taken in conjunction with the accompanying drawings and this Background.